US3769505A - Radioactive halogen monitoring system - Google Patents

Radioactive halogen monitoring system Download PDF

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Publication number
US3769505A
US3769505A US00234922A US3769505DA US3769505A US 3769505 A US3769505 A US 3769505A US 00234922 A US00234922 A US 00234922A US 3769505D A US3769505D A US 3769505DA US 3769505 A US3769505 A US 3769505A
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filter elements
gas
collecting
stream
filter
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US00234922A
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J Lee
W Alves
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General Electric Co
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General Electric Co
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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01T—MEASUREMENT OF NUCLEAR OR X-RADIATION
    • G01T7/00—Details of radiation-measuring instruments
    • G01T7/02—Collecting means for receiving or storing samples to be investigated and possibly directly transporting the samples to the measuring arrangement; particularly for investigating radioactive fluids
    • G01T7/04—Collecting means for receiving or storing samples to be investigated and possibly directly transporting the samples to the measuring arrangement; particularly for investigating radioactive fluids by filtration

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  • ABSTRACT A system of two or more filter-detectors for detecting radioactive halogens such as iodine in a gas stream also containing other radioactive substances such as radioactive noble gases.
  • the invention relates to the detection of radioactive substances and particularly to the monitoring of radioactive halogens such as iodine in the presence of radioactive noble gases such as fission product gases.
  • radioactive halogens such as iodine
  • fission product gases radioactive noble gases
  • the process of fission in the operation of a nuclear power plant results in the formation of fission products among which are radioactive iodine and radioactive noble gases such as krypton and xenon. These fission products are formed in the fuel and normally are retained in the sealed fuel rods.
  • small amounts of the fission gases and volatile fission products escape into the coolant.
  • small quantities of radioactive gases are formed by activation in the coolant.
  • iodine In addition to monitoring the gross radioactivity of the gases, vapors and particulates of the off-gas stream it is desirable to separately monitor the radioactivity of particular ones of these substances, for example, iodine.
  • the monitoring of iodine has been found to be very difficult because it constitutes but a small fraction of the off-gas stream and its radioactivity is masked by the greater radioactivity of the noble gases.
  • iodine can be captured and accumulated in an activated charcoal filter while the accompanying noble gases, though adsorbed and delayed in their passage through such a filter, are not accumulated therein.
  • a known sample amount of the off-gas stream can be passed through a charcoal filter for a given period of time.
  • the filter then can be flushed (with clean air for example) to remove any remaining noble gases and then after a time sufficient to let solid radioactive decay products of the gases (for instance cesium and rubidum) to decay to a sufficiently low level (their half lives being much shorter than most of the iodine) the radioactivity of the accumulated iodine can be measured. By relating this measurement to the sample amount and time the average contribution of the iodine over the sample period to the gross radioactivity of the off-gas stream can be determined. This approach to iodine monitoring is employed, for example, in the off-gas system of the aforementioned Schroeder et al article.
  • a serious disadvantage of such an approach is that the sampling period is undesirably long, for example, in the order of several days. It is an object of the invention to greatly reduce the sampling time. Another object is to eliminate the need of periodic removal and hapdling of the filter element.
  • a system including two (or more) iodine collecting filters and radiation detectors.
  • a sample stream of the gas to be monitored (such as the reactor off-gas) is pumped through a first one of the filters while a second filter is flushed with a purge gas and the radiation from the second filter is measured.
  • the sample stream is diverted from the first filter to the second filter and the first filter is flushed and measured.
  • the sample stream is again diverted to the first filter etc.
  • FIG. 1 is a schematic diagram of an iodine monitoring system in accordance with-the invention
  • FIG. 2 is a timing diagram of the operation of the system of FIG. 1;
  • FIG. 3 illustrates the inclusion of a differential circuit in the system
  • FIG. 4 illustrates the inclusion of a sample gas heater in the system
  • FIG. 5 is a schematic diagram of a system employing three filters.
  • FIG. 6 is a timing diagram of the operation of the system of FIG. 5.
  • the system of the invention comprises a pair of well-known activated charcoal filters 10(1) and 10(2), a pair of twoway valves 11(1) and 11(2), a pump 12, a pair of wellknown radiation detectors 13(1) and 13(2), for example, of the sodium iodide crystal type, a switch 14 for connecting the detectors 13(1) and 13(2) alternately to a pulse rate meter 16 (including an indicator l7) and a timer 18 for cyclically actuating the valves 11(1), 11(2) and the switch 14.
  • a pulse rate meter 16 including an indicator l-7
  • timer 18 for cyclically actuating the valves 11(1), 11(2) and the switch 14.
  • FIG. 2 shows the radioactivity, as detected at the filters 10(1) and 10(2) plotted against arbitrary time units.
  • the valve 11(1) is set so that sample gas from a sample gas input conduit 19 is fedthrough filter 10(1) wherein the iodine contained in the sample gas is trapped and the accompanying noble gas exhausted from the filter 10(1) through an output conduit 21 by pump 12.
  • valve 11(2) is set such that the filter 10(2) is being flushed with a purge gas (such as clean air, steam or the like) from a purge gas input conduit 22(2) and the switch 14 is set so as to connect detector 13(2) to the rate meter 16.
  • a purge gas such as clean air, steam or the like
  • valve 11(1) is actuated by the timer 18, via a link 23(1), to shut off the sample gas and to direct a purge gas from a purge gas input conduit 22(1) through the filter 10(1).
  • valve 11(2) is actuated by the timer 18, via a link 23(2) to feed sample gas through the filter 10(2); simultaneously, the timer 18, via a link 24, throws switch 14 to its alternate position to thereby connect the detector 13( 1) to rate meter 16.
  • valve 11(2) is actuated to flush the filter 10(2), and one cycle of operation is completed at the end of the tenth time unit when the valve 11(1) is again actuated to direct sample gas through filter (1) and the switch 14 is thrown to again connect detector 13(2) to rate meter 16.
  • each filter collects for four time units, is flushed for six time units and is monitored during the last five time units of each flushing cycle. This provides one time unit of flushing cycle overlap which serves to substantially purge the noble gases from a filter before the adjacent detector is connected to the rate meter.
  • the time units shown in FIG. 2 are arbitrary; however, it is contemplated that the collecting periods (of four time units) may be a fraction of time required by prior systems, for example, in the order of 10-30 seconds.
  • the present system provides a more prompt indication of the amount of iodine in the sample gas stream, especially as compared to the many hours, or even days, of collecting time of the known prior iodine monitoring systems.
  • the radioactivity detected at each filter increases with time (to the right) as more and more iodine is collected in the filters.
  • the measured radioactivity in the filters will reach a constant value at an equilibrium point where the rate of decrease of radioactivity due to decay equals the rate of radioactivity build-up due to the newly collected iodine. Any change in the amount of iodine in the sample gas will shift the equilibrium point and cause a corresponding change in the reading on the indicator 17.
  • a well-known differentiating circuit which, in effect, stores and divides the measurement of the previous monitoring period into the measurement of the current monitoring period.
  • Such a differentiating circuit can be connected to replace the rate meter 16 or it can be connected in parallel therewith as shown in FIG. 3 which illustrates a differentiating circuit 25, with an indicator 26, connected to the switch 14 in parallel with rate meter 16. (Suitable differentiating circuits are shown by WJ. Price in the above mentioned publication.)
  • the effectiveness of the iodine monitoring system of the invention can be increased by heating the sample gas before it is fed to the charcoal fiters. Heating of the sample gas is found to reduce the amount of noble gases residing in the filters and consequently their radioactive decay products, such as eesiurn and rubidium, with which they are in radioactive equilibrium, while not appreciably reducing the ability of the filters to collect and retain the iodine, thus reducing necessary cesium and rubidium decay times before measurement of iodine.
  • the temperature of the sample gas can be raised by installing a heater 27 in the sample gas input conduit 19 as illustrated in FIG. 4. Good results may be obtained by heating the sample gas to a temperature in the range of l50-250F.
  • system of the invention is described herein in connection with monitoring of reactor off-gases, the system is equally useful for other applications such as monitoring the iodine or other halogens in the atmosphere of reactor, heat exchanger or turbine containments or in reprocessing plants or for any other application requiring the detection of radioactive iodine or other halogens in the presence of radioactive noble gases or other substances which effectively can be flushed from the filters.
  • FIGS. 1 and 2 The concept of the invention exemplified in FIGS. 1 and 2 can be extended through the use of additional filter elements and associated valves and detectors.
  • a system using three filters i00(l)-100(3), with associated valves (1)-1l0(3), detectors l30(l)l30(3) and a three-position stepping switch is shown in FIG. 5. Operation of the system of FIG. 5 is illustrated by the timing diagram of MG. 6 wherein the collecting (C) and monitoring (M) periods are each of three time units duration while the flushing periods (F) are of six time units duration.
  • the additional filter allows a longer flushing and decay time before measurement for more complete purging of the noble gases from the filters.
  • a system for detecting radioactive halogen in a stream of sample gas also containing radioactive noble gas comprising: first and second charcoal filters each of said filters having an inlet and an outlet; means for discharging gas from the outlets of said filters; a source of said sample gas; a source of purge gas; a first valve having an outlet connected to said inlet of said first filter, an inlet connected to said source of sample gas and an alternate inlet connected to said source of purge gas; a second valve having an outlet connected to said inlet of said second filter, an inlet connected to said source of sample gas and an alternate inlet connnected to said source of purge gas; means for actuating said first and second valves; a first radiation detector located adja cent said first filter; and a second radiation detector located adjacent said second filter.
  • the system of claim 1 including a rate meter for counting and indicating the radiation events detected by said detectors; and a switch having a pole and first and second terminals, said pole being connected to said I rate meter, said first terminal being connected to said first detector and said second terminal being connected to said second detector.
  • said means for actuating includes timing means having a first actuating link connected to said first valve, a second actuating link connected to said second valve, and a third actuating link connected to said switch.
  • the system of claim 1 including means for increasing the temperature of said sample gas including a heater connected between said source of sample gas and said first and second valves.
  • the system of claim 1 including a differentiating circuit connected to said detectors for indicating the rate of change of radiation detected by said detectors.
  • a system for detecting radioactive halogen in a sample stream also containing other radioactive substances comprising: a plurality of filter elements having the capability of collecting and retaining said halogen and allowing said other substances to be substantially flushed therefrom by a purge stream; means for directing said sample stream in turn through successively different ones of said elements during successive collecting periods; means for directing said purge stream in turn through said successively different ones of said elements during successive flushing periods following said collecting periods; and means for detecting radiation in turn from said successively different ones of said elements during successive monitoring periods starting after the beginning of the flushing period and ending at least at the beginning of a next successive collecting period of each element.
  • the system of claim 6 including means for heating said sample stream to a temperature of l50-250F. before passage into said filter elements.
  • a method of detecting radioactive halogen in a gas stream also containing radioactive noble gas comprising the steps of:
  • the method of claim 11 including the step of heating said gas stream to a temperature of -250F before directing said gas stream through said filter elements.

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  • High Energy & Nuclear Physics (AREA)
  • Analytical Chemistry (AREA)
  • Physics & Mathematics (AREA)
  • Health & Medical Sciences (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • General Physics & Mathematics (AREA)
  • Chemical & Material Sciences (AREA)
  • Molecular Biology (AREA)
  • Spectroscopy & Molecular Physics (AREA)
  • Measurement Of Radiation (AREA)
  • Sampling And Sample Adjustment (AREA)
  • Monitoring And Testing Of Nuclear Reactors (AREA)
  • Treating Waste Gases (AREA)
US00234922A 1972-03-15 1972-03-15 Radioactive halogen monitoring system Expired - Lifetime US3769505A (en)

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US23492272A 1972-03-15 1972-03-15

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US (1) US3769505A (enrdf_load_stackoverflow)
JP (1) JPS5620510B2 (enrdf_load_stackoverflow)
DE (1) DE2312303C2 (enrdf_load_stackoverflow)
ES (1) ES412625A1 (enrdf_load_stackoverflow)
FR (1) FR2176417A5 (enrdf_load_stackoverflow)
GB (1) GB1412349A (enrdf_load_stackoverflow)
IT (1) IT981245B (enrdf_load_stackoverflow)

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4435644A (en) 1980-07-15 1984-03-06 Tokyo Shibaura Denki Kabushiki Kaisha Radioactive effluent gas monitoring apparatus
US6142024A (en) * 1997-10-23 2000-11-07 Huls Aktiengesellschaft Apparatus and method for sampling and IR-spectroscopic analysis of high-purity, hygroscopic liquids
US20100027013A1 (en) * 2008-08-04 2010-02-04 Hansen Anthony D A Method and apparatus for the analysis of materials
US9671324B2 (en) 2014-04-24 2017-06-06 Aerosol D.O.O. Method and apparatus to compensate analytical devices that collect constituents of interest on a filter for the effect of filter loading
US9697921B2 (en) 2013-07-19 2017-07-04 Areva Gmbh Ventilation system operating method for use during a serious incident in a nuclear plant

Families Citing this family (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR2456331A1 (fr) * 1979-05-11 1980-12-05 Commissariat Energie Atomique Dispositif de prelevement et de controle d'aerosols radioactifs
JPH0447650U (enrdf_load_stackoverflow) * 1990-08-30 1992-04-22
GB2314619B (en) * 1996-06-29 2000-10-18 Martin John Oliver Radioactive iodine monitor
WO2005029506A2 (en) * 2003-01-31 2005-03-31 Engineered Support Systems, Inc. Nbc filtration unit providing unfiltered and filtered air paths
JP6029099B2 (ja) * 2012-10-19 2016-11-24 日立造船株式会社 排水中の放射性セシウムの濃度を実質上連続的に測定する方法および装置
JP2014145644A (ja) * 2013-01-29 2014-08-14 Toshiba Corp ダスト放射線モニタ装置及びダスト放射線モニタ方法
CN111610546B (zh) * 2020-05-23 2022-03-15 陕西卫峰核电子有限公司 一种I-129与Kr-85探测信号甄别处理方法
CN111863295B (zh) * 2020-07-29 2022-04-15 中国舰船研究设计中心 一种船用多功能小型化集成式气载放射性监测系统

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2945127A (en) * 1954-10-25 1960-07-12 Phillips Petroleum Co Automatic process control with radioisotopes
US2951156A (en) * 1955-05-24 1960-08-30 Walter Kidde Nuclear Lab Inc Method and apparatus for predicting the residual life of adsorption beds
CA837735A (en) * 1970-03-24 M. Holford Richard Method and apparatus for monitoring a gaseous atmosphere for radioactive isotopes including organic iodine compounds
US3617709A (en) * 1969-03-28 1971-11-02 Japan Atomic Energy Res Inst Apparatus for detecting failures of nuclear fuel elements

Family Cites Families (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR1403811A (fr) * 1964-05-13 1965-06-25 Commissariat Energie Atomique Dispositif de détection de rupture de gaine

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CA837735A (en) * 1970-03-24 M. Holford Richard Method and apparatus for monitoring a gaseous atmosphere for radioactive isotopes including organic iodine compounds
US2945127A (en) * 1954-10-25 1960-07-12 Phillips Petroleum Co Automatic process control with radioisotopes
US2951156A (en) * 1955-05-24 1960-08-30 Walter Kidde Nuclear Lab Inc Method and apparatus for predicting the residual life of adsorption beds
US3617709A (en) * 1969-03-28 1971-11-02 Japan Atomic Energy Res Inst Apparatus for detecting failures of nuclear fuel elements

Cited By (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4435644A (en) 1980-07-15 1984-03-06 Tokyo Shibaura Denki Kabushiki Kaisha Radioactive effluent gas monitoring apparatus
US6142024A (en) * 1997-10-23 2000-11-07 Huls Aktiengesellschaft Apparatus and method for sampling and IR-spectroscopic analysis of high-purity, hygroscopic liquids
US20100027013A1 (en) * 2008-08-04 2010-02-04 Hansen Anthony D A Method and apparatus for the analysis of materials
US8411272B2 (en) * 2008-08-04 2013-04-02 Magee Scientific Corporation Method and apparatus for the analysis of materials
EP2151679A3 (en) * 2008-08-04 2013-08-14 Aerosol d.o.o. Method and apparatus for the analysis of materials
US9697921B2 (en) 2013-07-19 2017-07-04 Areva Gmbh Ventilation system operating method for use during a serious incident in a nuclear plant
US9671324B2 (en) 2014-04-24 2017-06-06 Aerosol D.O.O. Method and apparatus to compensate analytical devices that collect constituents of interest on a filter for the effect of filter loading

Also Published As

Publication number Publication date
JPS5620510B2 (enrdf_load_stackoverflow) 1981-05-14
ES412625A1 (es) 1977-10-16
IT981245B (it) 1974-10-10
DE2312303C2 (de) 1984-03-15
FR2176417A5 (enrdf_load_stackoverflow) 1973-10-26
GB1412349A (en) 1975-11-05
JPS493688A (enrdf_load_stackoverflow) 1974-01-12
DE2312303A1 (de) 1973-09-20

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